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Examining Potato Virus Y (PVY) in the First Field Season of the University of Minnesota Potato Breeding Program

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Examining Potato Virus Y (PVY) in the First Field Season of the University of Minnesota Potato Breeding Program View metadata, citation and similar papers at core.ac.uk brought to you by CORE provided by University of Minnesota Digital Conservancy Examining Potato Virus Y (PVY) in the First Field Season of the University of Minnesota Potato Breeding Program A Thesis SUBMITTED TO THE FACULTY OF UNIVERSITY OF MINNESOTA BY Jennifer Sue Flynn IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF MASTER OF SCIENCE Advisor: Dr. Christian A. Thill December 2013 © Jennifer Sue Flynn 2013 Acknowledgments I would like to thank my advisor Dr. Christian A. Thill for his support and contributions to my learning and to this research. I thank my committee members, Drs. Alan Smith and Linda Kinkel for their time, patience and advice that helped in the completion of this research. I thank Mr. Jeff Miller for all of his work in organizing, planting and harvesting the potatoes that were used for this research. I thank my husband Tim for his patience and attention to household chores when my attention was on my studies and research. I thank the following funding sources: 1) Northern Plains Potato Growers Association, 2) Minnesota Area II Potato Research and Promotion Council, 3) North Dakota Agricultural Experiment Station Nesson Valley Potato Research Farm 4) Minnesota Agricultural Rapid Response Fund, 5) Minnesota Agricultural Experiment Station, and 6) National Institute of Food and Agriculture # MN-21-019 i Dedication This theis is dedicated to my parents and grandparents, who taught me to value education and hard work. ii Abstract Potato virus Y (PVY) is a threat to the potato industry because potatoes infected with PVY have reduced yield and, in some cases, reduced tuber quality. Furthermore, PVY infection can cause seed potato lots to be downgraded or rejected. In the potato industry, the use of certified seed is the main control method used to reduce the incidence of PVY. In a potato breeding program, PVY infection can compromise the process of evaluating germplasm by masking the true genetic potential of potato genotypes. If PVY incidence is high in the first field season, when genetic variation of germplasm is at its maximum, high numbers of genotypes with potentially desirable traits may be discarded because of PVY infection; thus, reducing the genetic variability in this population. Prior to this study, the University of Minnesota Potato Breeding Program had not tested first field season breeding potatoes (nuclear seed) for PVY. This study investigated three different field locations and different time points of PVY testing during the first field season in the University of Minnesota Potato Breeding Program from 2007 to 2009 to estimate PVY incidence in the U of M Potato Breeding Program’s nuclear seed. Greenhouse-grown minitubers were planted in three locations (Becker, MN; Grand Forks, ND; and Williston, ND) for three years. The minitubers were organized into seven populations based on minituber source and market type: Colorado Reds, Colorado Russets, Colorado Whites, North Dakota Reds, North Dakota Russets, North Dakota Whites, and Oregon Mix. During the growing season, leaf samples were taken at random and tested for PVY using serological methods. There were high percentages (above 0.5%) of PVY in the first field season at all locations in all years. Over all locations and years, 326 of 3532 samples (9.2% of the samples) tested positive for PVY. The average PVY incidence was highest in leaf samples collected late in the growing season. The Grand Forks, ND location (leaves collected 30 Sept. 2008) had the highest percentage (32.7%) of leaf samples testing positive for PVY. The Becker, MN location (leaves collected 9 July 2009) had the lowest percent (0.8%) of leaf samples testing positive for PVY. Within the populations, the highest PVY incidence estimated in this 3-year study occurred in Grand Forks, MN; where 65.6% of leaves collected from the Colorado red population tested positive for PVY. Those leaves were collected late in the growing season (30 Sept. 2008) and were planted in the field near advanced breeding lines that may have been a source of inoculum. Considering these results, strategies iii for managing PVY in breeding programs are necessary. Strategies such as isolation planting, using barrier crops and using techniques to remove viruses from infected potato plants may be needed to reduce and eliminate PVY from a breeding program’s germplasm. Since PVY is such problem for the potato industry, it is important for breeding programs to develop PVY-resistant cultivars of various market types and uses that are acceptable to growers and potato processors. iv Table of Contents List of Tables .................................................................................................................................. vii List of Figures ................................................................................................................................ viii Literature review .............................................................................................................................. 1 Introduction ................................................................................................................................. 1 Potato Virus Y ............................................................................................................................... 2 Particle structure and composition ......................................................................................... 2 Distribution and host range ..................................................................................................... 3 Seed certification programs’ role in managing PVY ................................................................. 3 Economic importance of PVY in potato ................................................................................... 6 Strains of PVY ........................................................................................................................... 6 PVY virus-vector pathosystem ................................................................................................. 8 The asymptomatic expression of potato virus Y .................................................................... 10 Asymptomatic cultivars.......................................................................................................... 11 Reasons PVY has become a major problem in potato ........................................................... 14 Potato Breeding ......................................................................................................................... 15 Advancing clones ................................................................................................................... 15 Practices that influence PVY in a breeding program ............................................................. 16 Research Objectives ....................................................................................................................... 19 Materials and Methods .................................................................................................................. 19 Material ...................................................................................................................................... 19 Location descriptions ................................................................................................................. 19 Weather data ............................................................................................................................. 20 Leaf collection and PVY testing .................................................................................................. 20 Data Analysis .............................................................................................................................. 21 Weather analysis .................................................................................................................... 21 Location analysis .................................................................................................................... 21 Time analysis across locations ............................................................................................... 22 Field maps .............................................................................................................................. 23 Results ............................................................................................................................................ 23 v Weather ..................................................................................................................................... 23 Locations .................................................................................................................................... 24 Time ........................................................................................................................................... 25 Field Maps .................................................................................................................................. 25 Discussion ...................................................................................................................................... 26 Conclusions .................................................................................................................................... 30 Literature Cited .............................................................................................................................
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